<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
  <title>Document</title>
  <style>
    .a{
      color: red;
    }

    li{
      float: left;
      list-style: none;
      margin-left: 45px;
    }
    li:hover{
      cursor: pointer;
      text-decoration: underline;
    }
  </style>
</head>

<body>
  <div id="app">
    <ol>
      <li 
      v-for="(value,index) in list"
      @mouseover="i = index"
      @mouseout="i = ''"
      :class="index === i ? classN : ''">{{value}}</li>
    </ol>
  </div>
  <script>
    const app = new Vue({
      data: {
        list: ['游戏资料','内容中心','赛事中心','百态王者','社区互动','玩家支持','IP新游'],
        classN:'a',
        i:''
      }


    }).$mount('#app')
  </script>
</body>

</html>